Varroa

 

HARMFUL | NOT HARMFUL | UNCERTAIN

parasite; feeds on hemolymph of adult and developing honey bees; serious pest of the European honey bee worldwide

Name and classification

Varroa Oudemans, 1904

Taxonomy
Superorder Parasitiformes » Order Mesostigmata » Suborder Monogynaspida » Hyporder Dermanyssiae » Family Laelapidae » Genus Varroa

Type species
Varroa jacobsoni Oudemans, 1904

Common names
Varroa

Diagnosis

Female: Gnathosoma with 3 pairs hypostomal setae (Fig. 3). Idiosoma transversely oval in outline (Figs. 1, 2). Opisthosoma hypertrichous (Figs. 1, 2, 5). Exopodal IV, epigynal, and matapodal shields enlarged, covering almost all of ventral opisthosoma (Fig. 2). Epigynal and metapodal shields almost touching (Fig. 2). Anal opening ventral (Fig. 2).

Species identification

The following species are currently included in Varroa: Varroa destructor Anderson and Trueman, 2000; Varroa jacobosoni Oudemans, 1904; Varroa rindereri de Guzman and Delfinado-Baker, 1996; and Varroa underwoodi DelīŦnado-Baker and Aggarwal, 1987. Molecular and morphological treatment of these species is available in Anderson and Trueman, 2000.

Similar genera

Similar to Euvarroa but differs by (character states of Euvarroa are in parentheses): idiosoma transversely oval (not transversely oval); exopodal IV, epigynal, and matapodal shields enlarged, cover almost entire ventral opisthosoma (exopodal IV and epigynal shields not enlarged, not covering); and anal shield ventral, visible ventrally (anal shield terminal, not visible ventrally).

Distribution

Varroa destructor is a globally distributed parasite attacking managed colonies of the European honey bee worldwide (it has not yet been found in Australia).

Other species of Varroa are distributed in Asia (southern countries) and New Guinea. The most northern record is from South Eastern Russia (Varroa underwoodi).

Bee hosts

honey bees (Apis)

Host association level

Permanent

associated exclusively with bees or their close relative, wasps; cannot live without these hosts

Temporary

some life stages are associated with bees, while others are not

Facultative or opportunistic

can complete entire life cycle without bees or their close relative, wasps

permanent

Host associations, feeding, and dispersal

  • All active stages live in bee hives inside capped brood cells, where they parasitize developing honey bees by feeding on their hemolymph.
  • Active stages are protonymphs, deutonymphs, and adults. Larvae are non-feeding, pharate, and develop under egg shell.
  • Mite females disperse on adult bees, where they feed on host hemolymph.

Biology

This biological account was modified from Sammataro et al., 2000.

Several key morphological features help make Varroa a successful ectoparasite: It can survive off the host for 18 to 70 hours, depending on the substrate; the female’s chelicerae are structurally modified — the fixed digit is lacking and the moveable digit is a saw-like blade capable of piercing and tearing the host’s integument; the mite’s body is dorsoventrally compressed, allowing the mite to fit beneath the bee’s abdominal sclerites, thus lessening water loss from transpiration; and hiding there reduces Varroa’s vulnerability to grooming and to dislodgment during host activity.

Varroa females are often found on adult bees, which provide for dispersal and serve as short-term hosts. Varroa prefers young bees to older workers, probably because of the lower titer of the Nasonov gland pheromone geraniol, which strongly repels the mite. The mite pierces the soft intersegmental tissues of the bee’s abdomen or behind the bee’s head, and feeds on the hemolymph. When in an actively reproducing bee colony, the mite disembarks and seeks brood cells containing third-stage bee larvae. Varroa, which prefers drone larvae but also invades workers’ cells, is attracted to fatty acid esters, which are found in higher quantities on immature drones than on workers. Other known attractants are the aliphatic alcohols and aldehydes from bee cocoons and perhaps the larger volume of drone cells.

Most species in this genus are relatively benign parasites associated with honey bees in the wild. However, one species, Varroa destructor, has spread from Apis cerana to Apis mellifera, causing enormous bee losses. Varroa destructor can kill entire colonies of its unnatural host, the European honey bee Apis mellifera, while it does not kill colonies of its natural host, Eastern honey bee Apis cerana. This difference may be due to the presence of resistance against the mite developed by Apis cerana over evolutionary time.